I am in the proses of building a 260 rem here in South Africa by a local gun smith.
He asked if i wanted the ackley improved version but i dont know if the extra fps
will be worth the fire form. Want to shoot 140gn bergers at 800 yards.We also have
difficulty getting the dies for the AI.

Jasper, I have a 260ai and I can honestly say that the extra velocity you get from the improved cartridge is very welcome when you get to 800yds. Here in New Zealand you are often battling the wind across big valleys and being able to shoot 140gn VLDs with a high BC at 2950fps provides a noticeable advantage. Often and with the std 260, people use a lighter bullet to maintain velocity and this is a disadvantage when you get further out or there is some wind.